The present invention relates to a device for controlling an outlet valve during the engine brake mode, wherein the device comprises a hydraulic linkage between the outlet valve and the cam shaft, the hydraulic linkage being supplied with hydraulic pressure from a pressure source upon switching to the engine brake mode. The pressure source is comprised of an actuation piston which is actuated by one brake cam per cylinder arranged at the cam shaft that drives the inlet and outlet valves. The outlet valve is opened by the hydraulic pressure by lifting a working piston within the hydraulic linkage during the engine brake mode.
From German Offenlegungsschrift 39 22 884 a hydraulic linkage is known which is arranged between a cam shaft and an outlet valve and which serves during the engine brake mode to lift the outlet valve during the compression stroke in order to increase the braking power. The hydraulic linkage is comprised of a valve rod in which a working piston is movably arranged and which, with respect to the valve rod, has an axial stroke in the direction to a push rod. The axial stroke corresponds to the opening stroke of the outlet valve during the engine braking mode. For the purpose of lifting the outlet valve during the compression stroke a compression chamber is arranged below the working piston and is connected via pressure lines to an external pressure source which during the engine brake mode is driven by the cam shaft. The pressure source loads the working piston in a cyclic manner in order to open the outlet valve also during the compression stroke of the engine when the valve rod itself rests on the base circle of the outlet cam. When the outlet valve is opened during the exhaust stroke, the pressure chamber is without load from the pressure source so that the outlet valve, after exhausting the play between the working piston and the valve rod, is opened by the outlet cam during engine operation. Such a pressure source and control unit require a great constructive expenditure with high costs even when mass-produced. A combination of pressure source and control unit of identical construction can only be used for internal combustion engines with the same number of cylinders because when the number of cylinders of the combustion engine is changed, a change of the number of actuation pistons of the pressure source is also required.
It is therefore an object of the present invention to provide a device with a hydraulic linkage having a control unit that is designed such that it is applicable for internal combustion engines of any desired number of cylinders whereby the control unit itself must not be altered. A further object of the present invention is the elimination of outwardly arranged pressure lines for achieving a precise control of the outlet valve.